The present invention relates to artificial airways that medical personnel use for patient airway access. More particularly, the present invention relates to laryngeal mask airways that incorporate a cuff filled with a resilient foam-like material to effectively seal the connection between the artificial airway and the patient's airway.
Medical personnel use artificial airways for airway management in an effort to monitor and control gas flow to and from the patient's lungs. This includes gases used in the administration of anesthesia. Artificial airways can be connected to the patient's airway in various locations and with various mechanisms. The most common artificial airways consist of endotracheal catheters that are inserted through the larynx and into the patient's trachea. See, for example, U.S. Pat. Nos. 3,640,282 to Kamen et al. and 3,799,173, to Kamen. Other artificial airways are laryngeal masks positioned over the laryngeal opening. See, for example, U.S. Pat. Nos. 4,509,514 and 5,355,879 to Brain.
Conventional laryngeal masks provide a seal over the laryngeal opening by using a cushion or inflatable ring cuff that is inflated with air. This inflation process consumes valuable medical personnel time that could be dedicated to other functions beneficial to the patient. Furthermore, a cushion inflated in such a manner may create excessive pressure on the laryngeal rim resulting in tissue damage. A laryngeal mask that reduces the possibility of exerting excessive pressure on the airway tissue caused by excessive cuff inflation would be a welcome improvement in laryngeal masks.
Furthermore, when deflated, conventional inflatable ring cuffs are flexible and include a frontal portion or tip. The flexible nature of the frontal portion of the ring cuff may cause it to fold back during insertion of the conventional laryngeal mask into the patient's airway. This would prevent the inflatable ring cuff from forming an effective seal over the laryngeal opening. The conventional laryngeal mask airway must then be removed, re-prepared for insertion, and then reinserted. The patient would, in all probability, not breath and may not be ventilated during this interval. This could result in possible harm to the patient secondary to hypoxia. A cuff that effectively seals over the laryngeal opening, but has a frontal tip that is less likely to fold back would save valuable medical personnel time and be a useful advancement in laryngeal masks.
According to the present invention, a laryngeal mask airway is provided for use in patients having an airway and a larynx. The larynx has a laryngeal opening and a laryngeal rim surrounding the laryngeal opening.
The laryngeal mask airway of the present invention includes a catheter or air tube for the passage of gases, a pilot tube, and a laryngeal mask. The catheter includes a proximal end and a mask end spaced apart from the proximal end. The pilot tube includes a port end and a flow control end spaced apart from the port end. The laryngeal mask is attached to the mask end of the catheter. The laryngeal mask includes a back plate having an outer rim and a foam cuff attached to the outer rim. The port end of the pilot tube is attached to and opens into the foam cuff. The foam cuff includes a resilient material and a pliable sheath coupled to the back plate. The pliable sheath is formed to include an interior region and the resilient material is positioned to lie within the interior region. The resilient material expands and deflates between a deflated position and an expanded position to seal over the laryngeal opening.
The foam cuff is deflated by using a syringe or similar pressure-creating device to withdraw air out of the resilient material through the pilot tube. A pilot tube cap closes off the pilot tube to maintain the vacuum created in the resilient material.
Next, the laryngeal mask airway is inserted into the patient's airway and over the patient's laryngeal opening and rim. To inflate a previously deflated foam cuff, the pilot tube cap is removed and air enters the deflated resilient material through the pilot tube. The air is drawn into the foam cuff by negative pressure generated by an expansive nature of the deflated resilient material. The resilient material then expands and the foam cuff substantially forms a seal over the laryngeal opening and with the laryngeal rim.
The resilient material is yieldable and contacts and conforms to peaks and valleys that define the laryngeal rim. This contact does not create high pressure on the airway tissue that may be created by conventional inflatable ring cuffs. Thus, the foam cuff according to the present invention reduces the potential for damage to the laryngeal tissue.
According to another preferred embodiment of the present invention, the resilient material is contoured to include crests and canyons that generally follow the configuration of the tissues of the laryngeal rim. This contoured resilient material allows the cuff to reasonably match the configuration defined by the peaks and valleys of the laryngeal rim and U-shaped channels surrounding a portion of the laryngeal rim without relying exclusively on the expansive nature of the resilient material. This further reduces the potential pressures exerted on the laryngeal tissues, thus reducing tissue damage, while also creating a more effective seal.
The yieldable fit provided by the resilient material allows it to expand deeper into the valleys of the laryngeal rim and the U-shaped channels. The additional expansion into the valleys and U-shaped channels creates a locking barrier to motion perpendicular to the depth of the valleys and U-shaped channels. These barriers will increase the resistance against laryngeal mask motion in a direction perpendicular to the valleys' and U-shaped channels' depth. This resistance will increase with the additional expansion into the valleys and U-shaped channels provided by the use of contoured foam cuffs.
As mentioned previously, conventional laryngeal masks have frontal tips that have a tendency to fold back during insertion. The foam cuff tip according to the present invention, decreases in length while being deflated so that its tip length is less than that of a conventional inflatable ring cuff tip upon insertion into a patient's airway. This decreased tip length reduces the probability that the foam cuff tip will fold back during insertion when compared to the conventional inflatable ring cuff tip. An additional feature of a foam cuff is that it deflates inward. This decreases the foam cuff's width and allows for easier insertion into and through the mouth and pharynx in route to the patient's larynx.
Conventional inflatable ring cuff tips also develop a "hinging" tendency while in the deflated position that can further increase the likelihood of fold back if the cuff tip strikes the pharyngeal wall during insertion. A deflated foam cuff tip according to the present invention has less of a tendency to hinge back because its rigidity increases with deflation. Therefore, the decreased length and increased rigidity of the foam cuff tip reduces the likelihood that the tip will fold back upon engaging the patient's airway during insertion.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.